Alternate action snap mechanism



Ndv. 30, 1 954 M. w. EATON 2,695,524

ALTERNATE ACTION SNAP MECHANISM Filed Jan. 5, 1951 Invewfar ww wwcompression. mounting end 6 limits rotation of the toggle 8 in oneUnited States PatentOfilice ALTERNATE ACTION SNAP MECHANISM Malcolm W.Eaton, Freeport, 111., assignor to Minneapolis- Honeywell RegulatorCompany, Minneapolis, Minn., a corporation of Delaware ApplicationJanuary 5, 1951, Serial No. 204,568

Claims. (Cl. 74-100) This invention is concerned with a mechanismadapted to move to alternate positions with a snap action uponsuccessive motions in the same directions of reciprocable operatingmeans. Alternate action mechanisms have been known for a long time butthose on the market especially in the form of electrical switches havenot been satisfactory. In general they are made up of a multitude ofparts assembled together. This larger number of parts is to aconsiderable extent responsible for the inconsistency in operation dueto the accumulation of tolerances. In addition, these switches aregenerally built as cheaply as possible so the parts are not veryaccurately made and do not fit together as Well as they should. It isnot at all uncommon on purchase of such switches to find that they areinoperative before being installed. Such a situation is in fact socommon that purchasers frequently make allowance for such faultyswitches and purchase more than are absolutely needed in order to besure that they have enough workable switches.

It is among the objects of this invention to provide a reliable snapacting alternate action mechanism, to provide a snap acting alternatemechanism having a minimum number of parts, to provide a snap actingalternate action electrical switch without current carrying pivots, andto provide a mechanism of the type described that may be quickly andeasily assembled by unskilled labor. It is a further object of thisinvention to provide an alternate action snap acting mechanism in whichrotation of the toggle is accurately limited so as to provide long lifeby limiting the stresses in the snap acting spring mechanism. It is alsoan object of this invention to provide an alternate action snap actingmechanism in which the stresses resulting from limiting the rotation ofthe toggle are kept at the lowest practical minimum.

In the drawings:

Figure 1 is a side view partly broken away of a switch incorporatingthis invention;

Fig. 2 is a top view of the switch shown in Figure 1 with the button,operating mechanism and shell removed;

Fig. 3 is a perspective view of the toggle employed in the switch shownin Figs. 1 and 2;

Fig. 4 is a plan view similar to Fig. 2 showing another species of theinvention;

Fig. 5 is a sectional view along the line 5-5 of Fig. 4, and

Fig. 6 is a perspective view of the spring used in the switchshown inFigs. 4 and 5.

In the embodiment of this invention shown in Figs. 1 and 2 the snapspring 1 comprises tension members 2 and compression member 3 joinedtogether at end 4 which is free to move and upon which is mounted amovable contact 5. The tension members are also con- .nected by amounting end 6 having a straight edge 7 facing the free end 4 to form apivot for a toggle 8. The

end 6 of snap spring 1 is mounted in cantilever fashion as by rivets orpart punches 9 on a plate or anchor 10,

having integral therewith the terminal 11 into which is threaded theterminal screw 12. The toggle 8, also referred to as the alternator, inthis embodiment comprises a piece of electrical insulating materialhaving a seat 13 hearing against the edge 7 so that the toggle 8 pivotsthereon. A groove 14, spaced from and opening in the opposite directionfrom said seat 13, pivotally supports the unattached end 15 of'thecompression member 3 so that the compression member 3 is held in bowedAn abutment 16 engageable with the 2 direction while another abutment 17is engageable with the anchor 10 to limit rotation of the toggle 8 inthe opposite direction. These abutments are so located as to permit thegroove14 to carry the end 15 from one side to the other of the plane oftension members 2, or, as it may otherwise be expressed, to move thecompression member 3 through an axis of maximum stress or position ofunstable equilibrium, or overcenter with respect to the line of actionof tension members 2 to produce a snap action. The dihedral angle formedby the intersection of two surfaces 18 and 19 forms a ridge or apex 20parallel to the seat 13 and groove 14. A projection 21, spaced from theridge 20 on surface 18, forms a valley 22 with the surface 18. In likemanner, projection 23, spaced from ridge 20, forms with the surface 19 avalley 24. The ridge 20 is so located that the seat 13 is on a linesubstantially bisecting the angle between surfaces 18 and 19. The partspreviously mentioned .form a subassembly mounted in the U shaped base 25by sliding the anchor-10 from one end of the base into, a slot andgrooves (not shown) formed in the upstanding walls forming the legs ofthe U so that the terminal 11 and terminal screw 12 are outside the wallwhile the anchor 10 and the other parts are inside. A stop establishingan upper limit for movement of free end 4 is provided by a contact 26mounted on terminal 27 having a terminal screw 28 threaded into it. Thiscontact 26, ter minal 27 and screw 28 form another sub-assembly slippedinto a slot (not shown) in the other end of the U-shaped base 25, sothat the terminal 27 passes through the wall and screw 28 is outsidewhile the contact 26 is inside in position to be engageable by movingcontact 5. The lower stop is formed by contact 29 mounted on terminal 30having a terminal screw 31 threaded therein. This sub-assembly issimilarly mountecl'in a slot in the end of base 25. r

The operating mechanism shown in connection with the invention comprisesa spring 32 supported on ledges 33 in the base 25 which spring supportsa driver 34. A button 35 has a groove 36 to position the driver 34 onspring 32 in alignment with the pivot 7. The spring 32 biases the driver34 and button 35 toward their normal positions. The operating mechanismis retained on the switch mechanism and the switch mechanismsub-assemblies are prevented from coming out of the base 25 by a-shell37 in the form of an open rectangle having a flange 38 engageable with aflange 39 on the button 35 to retain said button 35 in properrelationship with the base 25. The rectangular portion of the shell 37fits around the open top of the U-shaped base 25 and rests 'upon steps40 thereon. Depending ends 41 of shell 37 cover the open ends of base 25preventing the subassemblies from becoming disassembled from base 25.Bars 42 on the shell 37 provide mounting means for the switch.

The ridge 20 on toggle 8 is so positioned that it moves from one side tothe other of a plane through the pivot 7 and thenormal position of thedriver 34 as the toggle 8 is rotated from one limiting position to theother. The projections 21 and 23 are so positioned that each alwaysremains on one side of this plane. The surfaces 18 and 19 arealternately positioned to form an obtuse angle with respect to the lineof motion of the driver 34. Rotation of toggle 8 is limited to an anglesubstantially smaller than the supplement of the dihedral angle formedby the surfaces 18 and 19 so that, as shown in Figure 1, when the button35 is depressed, the driver 34 engages the surface 19 and is deflectedagainst projection 23. Further movement of the button 35 causes thedriver 34 to exert a torque on toggle 8, rotating it clockwise to itslimiting position, with abutment 16 engaging mounting end 6, and somoving the compression member 3 upward overcenter causing the movablecontact 5 to snap from stationary contact 26 to stationary contact '29.When the button 35 is released, the driver returns to its normalposition without moving the toggle 8. The next time the button 35 isdepressed, the driver 34 engages surface 18 and is deflected againstprojection 22. Further movement of button 35 causes the driver 34 toexert a torque on toggle 8, rotating it counterclockwise to its limitingposition with abutment 17 engaging anchor 10.

This movesv the compression member 3 downward overcenter to the positionshown in Figure 1, causing the movable contact 5 to snap from stationarycontact 29 to stationary contact 26. When button is released spring 32returns driver $4 :ndbutton 35 m their normal positions and the switchparts are all again in the'position's wn ra r H r From a theoreticalstandpoint it isniost desirableto limit rotation of the toggle in such amanner that movement of the supported member is limited with respect tothe supportingrnember. Therefore; it is desirable to have the togglestop against the supporting member which may or m yi s d a re nf t fi inb l he species shown in Figs. 1, 2 and 3 thi s p'rinciplehas beenemployed satisfactorily because movement of the driver is limited bylimiting movement of the button. In some applications it isimpossible orimpractical to limit movement of the driver except by the toggle itself;When this condition isencountered, the construction described isundesirable from a practical standpointsince it subjects the supportingmember to severe bending stresses when it stops movement of theabutments and also because the toggle is at the same time subjected tosevere stress :at the pivot when lower abutment stops motion of thetoggle. Sometimes it is impractical to strengthen these parts, as inelectrical switches in which the toggle is made of plastic to insulatethe operating mechanism from the live switch parts. Size is limited andcosts must be kept down in order to meetcompetition so that morematerial cannot be used to strengthen the parts adequately. To meet thisdifiiculty, .the construction shown in Figs. 4, 5 and 6 may be used.While not as accurate in limiting toggle rotation, it limits the severestresses referredto with regard to Figs. 1,2 and 3 by having theabutments on the sarne side of the pivot as theforce applied by thedriver and by stopping against the more rigid base rather than thesupporting member.

In the embodiment,shownin lfigs. 4, Sand 6 the snap spring 43 shown inFig. 6 is made of leafspring material having a U-shaped slot to formelongated members 44 and tongue 45 interconnected atend 46 which; isfree to move and upon which is mounted contact 47.

.The opposite ends of'the elongated members a're connected by a bridge48 having a straight edge 49 on the side nearest the end 46 to act as apivot. The mounting portion 50 is connected to the elongated members 44by side members 51 The 'mounting portion 50, the side members 51 andthebridge 48 forrnthe boundaries of an aperture 52. The mounting portionSiland side members 51 are clamped between two U-shaped anchors 53 fastenedto the base .54 as by a screw 55 threaded into an insert (not shown)passing through base 54. The

toggle 56 pivoted atbearin'g 57 on straight. edge 4? has a groove 58supporting end 59 in pivotal fashion to stress tongue 45 in bowedcompression. The abutment 66 'on one side of the bearing 57 isengageabie withv base 54 to li it counterclo kwise rotation of toggle5'6. Abi itrnent 61 on the other side of bearing 57 is adapted to passthrough aperture 52 and engage base 54 a) limit clockwise rotation oftoggle 5 6, These ab it'inents are so positioned with respect to bearing57 v and groove 58 to p errnitrnovement of groove 5 8 frorr 1 one sideto the other of the plane of tension members 44 to move the tonguethrough an axis of maximum stress and so cause, the free end 46 to movewith a snap action from one limiting position to another. A ridge 62 andprojections 63 on the toggle 56 are similar to and perform the samefunction as the corresponding parts described in connection with Figs.1,2 and 3. Contact 64, fastened to base 54, by screw 65 threaded into ametal insert (not shown) passing through base 54, and contact 66,retained on the base 54 by screw 67 threaded into another metal insert(not shown) passing through base 54, serve as "stopsto limit tr'avel ofthe free end 46 Te'rminals 68 on the exterior of base .54 are retainedon the base by screws 69 threaded into the inserts mentioned above andserve to connect the switch to an external circuit. V i H Any suitableoperating mechanism such as that shown in Figure 1 may be employed withthis switch mechanisin, the switch mechanism operating inthe same manneras that described in connection with Figs. 1, 2 and 3 except thatrotationof the toggle 56 ,is v abutments 6t) and 61. engaging .bas'e54;It will thus b;e seen that the abutment 60 or 61 limiting rotation ofthe tq .5 is t e s m s f the. Pi 9 r2 t the force applied by the driverto move the toggle 56 in order to reduce the stress in the supportingmember 48 and in the toggle 8 whenever it is impossible or impracticalto limit movement of the driving member.

I claim:

1. In combination, a leaf spring having a pair of spaced side membersjoined at each end, a flexible tongue integral with a first of said endsand extending between said side members in spaced relation therefrom todefine therewith a U-shaped aperture, and a mounting portion at thesecond of said ends having an edge thereof extending transverselybetween said side members and forming a fulcrum, a toggle having twosurfaces intersecting to form a ridge and defining a dihedral angle,said toggle having projections extending outwardly respectively fromeach of said surfaces in spaced relation from said ridge, said togglebeing formed with a notch therein defining a bearing for pivotallymounting the toggle which is disposed in a plane substantially,bisecting said angle, abutments to limit rotation of said toggle aboutsaid pivot to an angle substantially smaller than the'supp'lement ofsaiddihed'ral angle, sai'd'tog'gle being formed with a groove spacedfrom the pivotal mounting of. the toggle, said toggle being pivotallymounted with said bearing on said fulcrum 'on and supporting the freeend of the tongue in said groove to how the tongue in compression andstress said side membersin tension, at base, means for immovablymounting the leafspring at said mounting portion thereof incantileverfashion on said base, a pair of stops limiting motion of said fi'r stend of the leaf spring positioned to permit the toggle groove to crossthe plane of said side members as said toggle is rotated between itslimiting positions to snap said first end of the leaf spring fromon'e'stop to the other, and a reciprocable driver operable to be moved towardsaid toggle pivot to engage one of said toggle surfaces and to bedeflected therealong into engagement with one of said projections tomove said toggle from one limiting position to the other. 7 i

2. An alternate action mechanism comprising a base, a flat snap springhaving a first portion immovably mounted on said base, said firstportion having an edge forming a fulcrum which is fixed with respect tosaid base, said snap spring being movable through a position of unstableequilibrium between two stable positions in response to movement of asecond portion of said snap spring with respect to said mounted firstportion of the snap spring, an alternator pivoted on said fulcrum onsaid first portion of the snap spring and operably connected to saidsnap spring to effect movement of said second portion thereof,projections on said alternator disposed at opposite sides of the pivottherefor, and a driver re'ciprocable with respect to said base inadire'c'tion perpendicular to the face of said snap sprin and operativeto engage said projections alternately to rotate said alternator inopposite directions and move said snap spring alternately from onestable position to the other.

3. A snap acting switch comprising 'a base, a pair of spaced opposedstops mounted on said base, at least one of said stops defining a fixedcontact, a flat snap spring mounted in cantilever fashion at one end onsaid base and at its other end carrying a mobile contact movable betweensaid spaced opposed stops for engagement alternately therewith, said oneend of said s'na'pfs'pring having an edge which is fixed with respect tosaid base and forms a fulcrum, said snap spring including a flexiblemember spaced from the mounted end of the snap spring andinterconnectedwith the contact c'arrying movable end of the snap spring,an alternator pivoted on said fulcrum on said one end of the snap springand in spaced relation from its pivotal mounting engaging the end ofsaid flexible member remdte from the contact-carryin'g movable end ofthe snap spring for effecting snap action movement of said movableendofthe snap spring to move said mobile contact substantially directlyaway from one of said stops into engagement with the other of saidstops, projections on said alternator disposed on opposite sides of thepivotal mounting for the alternator, and a driver reciprocable withrespect to said base in a direction perpendicular to the face of saidsnap spring and operative to engage said projections alternately uponsuccessive icipiocations of the driver to rotate said alternator inopposite directions and move said mobile contact from one stop toanother.

4. In combination, a leaf spring having a pair of spaced side membersand end members integrally joined with the side members at each end, aflexible tongue integral with a first of said end members and extendingbetween said side members in spaced relation therefrom to definetherewith a U-shaped aperture, the second of said end members having anedge thereof extending transverse said side members and forming afulcrum, a base, means for immovably securing said second end member tosaid base and supporting said fulcrum in fixed relation to said base, atoggle having a first pair of surfaces intersecting to form a ridge,projections on said toggle extending outwardly respectively from each ofsaid surfaces in spaced relation to said ridge, said toggle having asecond pair of intersecting surfaces defining a notch the apex of whichis disposed substantially in the plane bisecting the angle between saidfirst pair of surfaces, said second pair of surfaces diverging relativeto a plane through the apex of said notch and perpendicular to the planebisecting the angle between said first pair of surfaces, said togglehaving a groove therein spaced from said notch and opening in adirection opposite thereto, said toggle being pivotally mounted on saidleaf spring with the apex of said notch seated on said fulcrum andsupporting the free end of said tongue in said groove to bow the tonguein compression and stress said side members in tension, said second pairof surfaces providing abutments to limit rotation of said toggle aboutsaid fulcrum, a pair of stops for limiting motion of the free end ofsaid leaf spring positioned to permit the toggle groove to cross theplane of said side members as said toggle is rotated between itslimiting positions to snap the free end of the leaf spring from one stopto the other, and a reciprocable driver operable to be moved toward saidtoggle fulcrum to engage said toggle surfaces and be deflectedtherealong into engagement with one of said projections to move saidtoggle from one limiting position to the other.

5. The combination of claim 4 wherein said means for securing saidsecond end member to said base includes a support plate secured to saidsecond end member and underlying said second end member adjacent saidfulcrum, and means for fixedly securing said support plate to said base.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,502,785 Kerwin July 29, 1924 2,021,041 Altamura Nov. 12,1935 2,295,484 Krieger Sept. 8, 1942 2,460,087 Hollis Jan. 25, 19492,537,682 Ljungfeldt Jan. 9, 1951 FOREIGN PATENTS Number Country Date985,620 France Mar. 14, 1951

